October 19

1856 – Biologist Edmund Beecher Wilson is born, noted for being the first scientist to publish photographs illustrating how a cell divides.
1900 – Max Planck discovers Planck's law of black-body radiation.

• A black-body is an idealized object which absorbs and emits all radiation frequencies.

1910 – Birth of Subrahmanyan Chandrasekhar, Indian-born astrophysicist, who was awarded the Nobel prize in physics for his studies on the physical processes important to the structure and evolution of stars.